+David and Ben
On Tue, Dec 06, 2022, Yu Zhang wrote:
> Simplify the code by introducing a wrapper, mmu_is_direct(),
> instead of using vcpu->arch.mmu->root_role.direct everywhere.
>
> Meanwhile, use temporary variable 'direct', in routines such
> as kvm_mmu_load()/kvm_mmu_page_fault() etc. instead of checking
> vcpu->arch.mmu->root_role.direct repeatedly.
I've looked at this patch at least four times and still can't decide whether or
not I like the helper. On one had, it's shorter and easier to read. On the other
hand, I don't love that mmu_is_nested() looks at a completely different MMU, which
is weird if not confusing.
Anyone else have an opinion?
> No functional change intended.
>
> Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
> ---
> arch/x86/kvm/mmu/mmu.c | 26 +++++++++++++-------------
> arch/x86/kvm/x86.c | 9 +++++----
> arch/x86/kvm/x86.h | 5 +++++
> 3 files changed, 23 insertions(+), 17 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 4736d7849c60..d2d0fabdb702 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -2280,7 +2280,7 @@ static void shadow_walk_init_using_root(struct kvm_shadow_walk_iterator *iterato
>
> if (iterator->level >= PT64_ROOT_4LEVEL &&
> vcpu->arch.mmu->cpu_role.base.level < PT64_ROOT_4LEVEL &&
> - !vcpu->arch.mmu->root_role.direct)
> + !mmu_is_direct(vcpu))
> iterator->level = PT32E_ROOT_LEVEL;
>
> if (iterator->level == PT32E_ROOT_LEVEL) {
> @@ -2677,7 +2677,7 @@ static int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva)
> gpa_t gpa;
> int r;
>
> - if (vcpu->arch.mmu->root_role.direct)
> + if (mmu_is_direct(vcpu))
> return 0;
>
> gpa = kvm_mmu_gva_to_gpa_read(vcpu, gva, NULL);
> @@ -3918,7 +3918,7 @@ void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu)
> int i;
> struct kvm_mmu_page *sp;
>
> - if (vcpu->arch.mmu->root_role.direct)
> + if (mmu_is_direct(vcpu))
> return;
>
> if (!VALID_PAGE(vcpu->arch.mmu->root.hpa))
> @@ -4147,7 +4147,7 @@ static bool kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
>
> arch.token = alloc_apf_token(vcpu);
> arch.gfn = gfn;
> - arch.direct_map = vcpu->arch.mmu->root_role.direct;
> + arch.direct_map = mmu_is_direct(vcpu);
> arch.cr3 = vcpu->arch.mmu->get_guest_pgd(vcpu);
>
> return kvm_setup_async_pf(vcpu, cr2_or_gpa,
> @@ -4157,17 +4157,16 @@ static bool kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
> void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
> {
> int r;
> + bool direct = mmu_is_direct(vcpu);
I would prefer to not add local bools and instead due a 1:1 replacement. "direct"
loses too much context (direct what?), and performance wise I doubt it will
influence the compiler.
